6 
BULLETIN 1323, U. S. DEPARTMENT OF AGRICULTURE 
When dissolved in water, pectins of high- jellying quality produced 
a very viscous solution, while the inferior pectins showed only a 
slight viscosity. Check tests using two and four times the quan- 
tities of acid, pectin, etc., gave the same results. 
Table 4 shows the results obtained by one extraction of five 370- 
grani samples of finely ground lemon peel, with a 0.1 per cent citric 
acid solution, varying the heating period. 
Table 4. — Results of a single extraction of lemon peel with 0.1 per cent citric acid, 
varying the time of heating 
Sample 
Temper- 
Time of 
Pectin 
Pectin 
for a 
good jelly 
No. 
ature 
heating 
in peel 
°C. 
Minutes 
Per cent 
Per cent 
1 
98 
15 
0.73 
. 0.3 
2 
98 
45 
1.24 
.3 
3 
98 
to 
1.65 
.4 
4 
98 
120 
2.10 
.4 
5 
70 
240 
.84 
.3 
Table 5 gives the results of two 3-hour extractions of two 680- 
gram samples of lemon peel, varying the acidity. 
Table 5. — Results of two S-hour extractions of lemon peel at 70° C. 
acidity 
varying the 
Sample 
No. 
Extraction 
Acidity 
(citric 
acid) 
Pectin 
in peel 
Pectin 
for a good 
jelly 
1 
First 
Per cent 
0.09 
.04 
.36 
Per cent 
0.23 
.32 
.46 
Per cent 
0.5 
1 
.5 
2 
First 
.4 
2 
.37 . 57 
.3 
The results of two half-hour extractions of a 330-gram lot of lemon 
peel, using distilled and tap water, are given in Table 6. 
Table 6. — Results of two half-hour extractions of lemon peel with 0.5 per cent 
citric acid at 98° C, using distilled and tap water 
Sample 
No. 
Extraction 
Water 
Pectin 
i in peel 
Pectin for 
a good 
jelly 
1 
First 
Distilled 
Per cent 
. 1.07 
Per cent 
0.2 
1 
Second. 
do 
1.44 
.3 
2 
First __ . . __ 
Tap 
do 
1.20 
1.23 
.3 
2 
Second,.. 
.3 
To ascertain the effect of low acidity on the quality of the product, 
a 1,950-gram lot and a 470-gram lot of orange peel were extracted 
twice at 98° C, with varying proportions of acid. 
